Thin film structure with controlled lateral thermal spreading in the thin film

ABSTRACT

An apparatus includes a non-metallic interlayer between a magnetic data storage layer and a heat sink layer, wherein interface thermal resistance between the interlayer and the heat sink layer is capable of reducing heat flow between the heat sink layer and the magnetic data storage layer. The apparatus may be configured as a thin film structure arranged for data storage. The apparatus may also include thermal resistor layer positioned between the interlayer and the heat sink layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/435,793 filed on Mar. 30, 2012, now U.S. Pat. No. 8,576,515, which isa continuation-in-part application of U.S. application Ser. No.12/962,928, filed Dec. 8, 2010, now U.S. Pat. No. 8,149,539, which is acontinuation application of U.S. application Ser. No. 11/707,280, filedFeb. 16, 2007, now U.S. Pat. No. 7,869,162, to which priority isclaimed, and which are hereby incorporated herein by reference in theirentireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with United States Government support underAgreement No. 70NANB1H3056 awarded by the National Institute ofStandards and Technology (NIST). The United States Government hascertain rights in the invention.

FIELD OF THE INVENTION

The present invention relates to thin film structures, and moreparticularly, relates to a thin film structure with controlled lateralthermal spreading in the thin film.

BACKGROUND INFORMATION

Heat assisted magnetic recording (HAMR) is one type of data storage thathas been proposed as a solution for increasing the areal density ofrecording data. HAMR generally refers to the concept of locally heatinga recording medium to reduce the coercivity of the medium so that anapplied magnetic writing field can more easily direct the magnetizationof the recording medium during the temporary magnetic softening of therecording medium caused by the heat source. HAMR allows for the use ofsmall grain media, which is desirable for recording at increased arealdensities, with a larger magnetic anisotropy at room temperature toassure sufficient thermal stability.

HAMR media usually requires a well-controlled thermal profile in orderto achieve high track density and provide a good thermal gradient forrecording. The use of a heat sink layer in the media has been proposedin order to conduct or direct heat away from the recording layer afterwriting to limit thermal erasure. However, the heat sink not onlyconducts heat vertically but also conducts heat laterally. Therefore,employing a media having a heat sink layer can result in the mediaexhibiting lateral thermal spreading. This lateral thermal spreadingduring the writing process limits the track density and the size of databits.

In order to achieve additional increases in data storage capacities,there remains a need for further reduction in the size of data bitswritten in storage media.

SUMMARY OF THE INVENTION

In one aspect an apparatus includes a non-metallic interlayer between amagnetic data storage layer and a heat sink layer, wherein interfacethermal resistance between the interlayer and the heat sink layer iscapable of reducing heat flow between the heat sink layer and themagnetic data storage layer.

In another aspect, an apparatus includes a thermal resistor layerbetween a magnetic data storage layer and a heat sink layer, and anon-metallic interlayer between the magnetic data storage layer and thethermal resistor layer, wherein interface thermal resistance between theinterlayer and the magnetic data storage layer is capable of reducingheat flow from the heat sink layer to the magnetic data storage layer.

In yet another aspect, a system includes a heat assisted magneticrecording head, and a heat assisted magnetic recording medium positionedadjacent the heat assisted magnetic recording head, the heat assistedmagnetic recording medium including: a non-metallic interlayer betweenadjacent layers, wherein the adjacent layers include a magnetic storagelayer and a heat sink layer, wherein interface thermal resistancebetween the interlayer and at least one of the adjacent layers iscapable of reducing heat flow between the heat sink layer and themagnetic data storage layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial representation of a data storage device that mayutilize a thin film structure, e.g. a recording media, constructed inaccordance with an embodiment of the invention.

FIG. 2 is a schematic representation of a heat assisted magneticrecording system constructed in accordance with an embodiment of theinvention.

FIG. 3A is a schematic side view of a perpendicular magnetic recordingmedium in accordance with an embodiment of the invention.

FIG. 3B is a schematic side view of a longitudinal magnetic recordingmedium in accordance with an embodiment of the invention.

FIG. 3C is a schematic side view of a tilted magnetic recording mediumin accordance with an embodiment of the invention.

FIG. 4 is a schematic side view of a thin film structure in accordancewith an embodiment of the invention.

FIG. 5A is a schematic side view of another thin film structure inaccordance with an embodiment of the invention.

FIG. 5B is a graphical representation of thermal resistor layerthickness versus the full width half maximum (FWHM) of the thermalprofile for the thin film structure of FIG. 5A.

FIG. 6A is a graphical representation of the X-position of the FWHM of aspinning thin film structure.

FIG. 6B is a graphical representation of the Y-position of the FWHM of aspinning thin film structure.

DETAILED DESCRIPTION

In one aspect, the present invention relates to thin film structures. Invarious embodiments, the thin film structure can be used in a datastorage media such as, for example, magnetic, magneto-optical or HAMRrecording media. In another aspect, the thin film structure can be usedas a perpendicular, longitudinal or tilted recording medium of a datastorage system.

FIG. 1 is a pictorial representation of a data storage system 10 thatcan utilize a thin film structure in accordance with an embodiment ofthis invention. The data storage system 10 includes a housing 12 (withthe upper portion removed and the lower portion visible in this view)sized and configured to contain the various components of the datastorage system 10. The data storage system 10 includes a spindle motor14 for rotating at least one storage media, such as a magnetic recordingmedium 16, which may be a perpendicular, longitudinal and/or tiltedmagnetic recording medium, within the housing 12. At least one arm 18 iscontained within the housing 12, with each arm 18 having a first end 20with a recording head or slider 22, and a second end 24 pivotallymounted on a shaft by a bearing 26. An actuator motor 28 is located atthe arm's second end 24 for pivoting the arm 18 to position therecording head 22 over a desired sector or track 27 of the disc 16. Theactuator motor 28 is regulated by a controller, which is not shown inthis view and is well known in the art.

FIG. 2 is a partially schematic side view of a data storage writeelement, such as, for example, recording head 22 and a data storagemedia such as, for example, recording media 16. Although an example ofthe invention is described herein with reference to recording head 22 asa HAMR head and the media 16 as a magnetic recording medium for use inassociation with the HAMR head, it will be appreciated that aspects ofthe invention may also be used in conjunction with other type recordingsystems, such as, for example, magneto-optical recording systems. Inaddition, it will be appreciated that the invention may be used inassociation with any suitable type of data storage system and is notlimited to the examples and illustrations set forth herein.

Still referring to FIG. 2, the HAMR head 22 may include a writer sectioncomprising a main write pole 30 and a return or opposing pole 32 thatare magnetically coupled by a yoke or pedestal 35. Flux (H) is directedfrom the main pole 30 into the recording media 16 and can be returned tothe opposing pole 32. A magnetization coil 33 may surround the yoke orpedestal 35 for energizing the HAMR head 22. The recording media 16 ispositioned adjacent to or under the HAMR head 22 for movement, forexample, in the direction of arrow A. The HAMR head 22 also may includea read section, not shown, which may be any conventional type transducerfor reading data. The read section may include, for example, aconventional giant magneto-resistance (GMR) reader, inductive reader,magneto-optical reader, or the like as is generally known in the art.

The HAMR head 22 may also include structure to heat the magneticrecording media 16 proximate to where the write pole 30 applies themagnetic write field H to the recording media 16. Such structure forHAMR can include, for example, an optical waveguide, schematicallyrepresented by reference number 51, in optical communication with alight source 52. The light source 52 may be, for example, a laser diode,or other suitable laser light sources for coupling a light beam 54 intothe waveguide 51.

FIG. 2 further illustrates a partially schematic side view of themagnetic recording media 16 constructed in accordance with an embodimentof the present invention. The magnetic storage media 16 can comprise aheat sink layer 44 formed on a substrate 45, a magnetic layer 40, suchas a recording layer, and a thermal resistor layer 42 positioned betweenthe heat sink layer 44 and the magnetic layer 40. During the writingprocess, heat is directed into the magnetic layer 40 in order to reducethe coercivity of the magnetic layer 40. Heat applied to the surface ofthe magnetic layer 40 adjacent the air bearing surface (ABS) of the mainwrite pole 30 will propagate through the magnetic layer 40 and may causethermal erasure of areas in the magnetic layer 40 adjacent the portionbeing currently written. In order to conduct or direct applied heat awayfrom the magnetic layer 40, the heat sink layer 44 is positioned belowthe magnetic layer 40 to draw heat away from the magnetic layer 40. Inaddition, a thermal resistor layer 42 is positioned to minimize orreduce the flow of heat from the heat sink layer 44 back into themagnetic layer 40.

Referring again to FIG. 2, the magnetic layer 40 can comprise, forexample, at least one of FePt, FePt alloys, FePd, FePd alloys, CoPt,CoPt alloys, Co/Pt multilayers, or Co/Pd multilayers. The magnetic layer40 also can include any of the aforementioned alloys and materials withoxides such as, for example, Co₂O₃, SiO₂, NiO, TiO₂, ZrO₂ or SnO₂. Inone example, the magnetic layer 40 can have a thickness in the range ofabout 10 nm to about 20 nm.

The heat sink layer 44 can comprise a thermally conductive material,such as a material having a thermal conductivity greater than about 20W/(mK). Example heat sink layer 44 materials can include Au, Ag, Al, Cu,W, Ru, Cr, Mo, Cu alloys, Ag alloys, or AU alloys. The heat sink layer44 can have a thickness in the range of, for example, about 20 nm toabout 2 mm.

Still referring to FIG. 2, the thermal resistor layer 42 is disposedbetween the magnetic layer 40 and the heat sink layer 44 to allow heatto flow from the magnetic layer 40 into the heat sink layer 44 whileminimizing or reducing the flow of heat from the heat sink layer 44 backto the magnetic layer 40. The thermal resistor layer 42 can comprise amaterial having a low thermal conductivity, such as, for example, lessthan about 5 W/(mK). Example thermal resistor layer materials includeoxides, nitrides, borides, carbides, or amorphous materials. Suchmaterials can include, for example, at least one of Al₂O₃, SiO₂, WO₃,Ta₂O₅, Nb₂O₅, ZrO₂, SiN, NiP or TiN. In one aspect, the thermal resistorlayer materials can be a low thermal conductivity material as well as bea soft magnetic material including, for example, FeCoB, CoZrNi, orCoTaFe. The thermal resistor layer 42 can have a thickness in the rangeof about 0.25 nm to about 50 nm.

As shown in FIG. 3A, the magnetic recording medium 16 can be aperpendicular recording medium, as indicated by the orientation of themagnetic grains 29A. As shown in FIG. 3B, the magnetic recording medium16 can be a longitudinal recording medium, as indicated by theorientation of the magnetic grains 29B. As shown in FIG. 3C, themagnetic recording medium 16 can be a tilted recording medium, asindicated by the orientation of the magnetic grains 29C.

FIG. 4 illustrates an additional aspect of a thin film structure in theform of a magnetic recording media 116. An interlayer 146 can bedisposed between the magnetic layer 140 and the heat sink layer 144. Inthe example of FIG. 4, the interlayer 146 is disposed between themagnetic layer 140 and the thermal resistor layer 142. The thermalresistor layer 142 can have a thickness in the range of about 0.25 nm toabout 50 nm. The interlayer 146 serves to improve the microstructure andmagnetic properties of the magnetic layer 140. More specifically, theinterlayer 146 can assist in developing the desired orientation,epitaxy, grain size and/or grain separation in the magnetic layer 140.The interlayer 146 can include, for example, Ru, Ru alloys, an oxidesuch as MgO, or a nitride such as TiN. The interlayer 146 can have athickness, for example, in the range of about 1 nm to about 30 nm. Inanother aspect, more than one interlayer may be disposed between themagnetic layer 140 and the thermal resistor layer 142.

Interface resistance refers to thermal resistance between two layers ofdifferent materials, for example, a metal and non-metal. The thermalresistance between the metal and non-metal layer is caused by theinterface effect of different means of thermal conductivity in the layermaterials. For example, in metal, heat is conducted by both electronsand the material lattice, while in non-metals, the heat is conductedprimarily via the material lattice. This results in an effective thermalresistor when heat is being conducted across such interface.

Interface resistance can provide the thermal resistance between a metalstorage layer and a non-metal interlayer, or the thermal resistancebetween a non-metal interlayer and a metal heat sink.

In media structures with an oxide (such as MgO) or nitride (such as TiNetc.) as the interlayer (as shown in FIG. 4, item 146), the interfaceresistance between the interlayer and the magnetic layer 140 could beused to provide the desired thermal resistance. In such structures, theactual thermal resistor layer (as shown in FIG. 4, item 142) thicknesscould be reduced to a range from 0 to 20 nm.

If no thermal resistor layer is present, the interface resistancebetween the interlayer and the heat sink layer 144 could be used toprovide the desired thermal resistance.

As will be appreciated by those skilled in the art, an overcoat layer,one or more seedlayers and/or other layers typically used to constructthin films may also be used in the thin film structure.

A sample thin film structure 216, shown in FIG. 5A, was constructed bydepositing a 3 nm Ta seedlayer 212 on a glass substrate 210, depositinga 600 nm CuZr heat sink layer 244 on the seedlayer 212, depositing aZrO₂ thermal resistor layer 242 of varying thickness T on the heat sinklayer 244, depositing a 3 nm Ta adhesion layer 243 on the thermalresistor layer 242, depositing a 5 nm Ru1 (low pressure processed) firstinterlayer 246 a on the adhesion layer 243, depositing a 15 nm Ru2 (highpressure processed) second interlayer 246 b on the first interlayer 246a, and depositing a 14 nm Co/Pt magnetic layer 240 on the secondinterlayer 246 b.

In order to determine the thermal profile of the thin film 216illustrated in FIG. 5A, an XY scanning pump probe device was set to apump laser spot size of 532 nm (FWHM) and a probe laser beam size of 405nm (FWHM). The scanning pump probe scans the plane of the thin film byvarying the incident angle and incident pitch of the probe, whichproduces a translation of the focused laser spot. Using known pump probetechniques, the probe measures the reflectivity of the thin film. Inoperation, the pump causes a temperature change in the thin film thatcauses a corresponding change in the reflectivity of the thin film. Thechange in the reflectivity is measured by the probe signal and,therefore, the scanned probe signal is capable of measuring the thermalprofile in the thin film caused by the pump. The obtained thermalprofile is a convolution of the spatial thermal profile in the thin filmgenerated by the pump and the spatial profile of the probe.

The thin film structure 216 was tested using the XY scanning pump probeand FIG. 5B graphically illustrates the FWHM of the measured thermalprofile versus the thermal resistor layer 242 thickness T. The presenceof the thermal resistor layer 242 results in a reduction of the FWHM andminimizes re-heating effects that occur far away from the thermalsource. For example, the measured FWHM is approximately 540 nm for athermal resistor layer thickness of T=10 nm to 20 nm, which is smallerthan the measured FWHM value of approximately 800 nm for T=5 nm andapproximately 1100 nm for T=0 nm (i.e. no thermal resistor layer).

To illustrate that the thin film structure 216 can confine the lateralthermal profile when spinning, i.e. when the structure 216 is formed asa recording media that would be spinning during writing/reading, thesample thin film was rotated at approximately 11 m/s and the thermalprofile was measured. The measured thermal profile was found to remainsubstantially symmetric when rotated. This is illustrated in FIGS. 6Aand 6B where the FWHM (i.e. the Pw50) along both the X-axis and theY-axis are substantially identical. This confirms that the thermalresistor layer is able to reduce and confine the lateral thermal profileor spreading when the structure is spinning.

Whereas particular aspects of this invention have been described abovefor purposes of illustration, it will be evident to those skilled in theart that numerous variations of the details of the present invention maybe made without departing from the invention as defined in the appendedclaims.

What is claimed is:
 1. An apparatus, comprising: a magnetic data storage layer; a heat sink layer; and an interlayer between the magnetic data storage layer and the heat sink layer, the interlayer configured to facilitate a first heat flow from the magnetic data storage layer to the heat sink layer and a second heat flow from the heat sink layer to the magnetic data storage layer, wherein a rate of the first heat flow is greater than a rate of the second heat flow.
 2. The apparatus of claim 1, wherein the interlayer comprises an oxide or a nitride.
 3. The apparatus of claim 1, wherein the interlayer comprises a boride or a carbide.
 4. The apparatus of claim 1, wherein the interlayer comprises an amorphous material.
 5. The apparatus of claim 1, wherein the interlayer comprises a soft magnetic material.
 6. The apparatus of claim 1, wherein the interlayer comprises at least one of Al₂O₃, SiO₂, WO₃, Ta₂O₅, Nb₂O₅, ZrO₂, SiN, NiP, TiN, FeCoB, CoZrNi, and CoTaFe.
 7. The apparatus of claim 1, wherein the interlayer comprises Ru or an Ru alloy.
 8. The apparatus of claim 1, wherein: the interlayer comprises an oxide or a nitride; and the heat sink layer comprises Au, Ag, AI, Cu, W, Ru, Cr, Mo, a Cu alloy, an Ag alloy or an Au alloy.
 9. The apparatus of claim 1, wherein: the interlayer comprises an oxide or a nitride; and the magnetic data storage layer comprises at least one of FePt, an FePt alloy, FePd, an FePd alloy, CoPt, a CoPt alloy, a Co/Pt multilayer or a Co/Pd multilayer.
 10. The apparatus of claim 1, wherein the interlayer layer has a thickness in the range of about 0.25 nm to about 50 nm.
 11. The apparatus of claim 10, wherein the heat sink layer has a thickness in the range of about 20 nm to about 2 mm.
 12. The apparatus of claim 1, wherein the interlayer has a thermal conductivity of less than about 5 W/(mK).
 13. The apparatus of claim 12, wherein the heat sink layer has a thermal conductivity of greater than about 20 W/(mK).
 14. An apparatus, comprising: a magnetic data storage layer; a heat sink layer; and an interlayer comprising MgO between the magnetic data storage layer and the heat sink layer, the interlayer configured to encourage heat flow from the magnetic data storage layer to the heat sink layer and resist heat flow from the heat sink layer to the magnetic data storage layer.
 15. The apparatus of claim 14, wherein: the heat sink layer comprises Au, an Au alloy, Ag, an Ag alloy, Al, Cu, a Cu alloy, W, Ru, Cr, or Mo; and the magnetic data storage layer comprises at least one of FePt, an FePt alloy, FePd, an FePd alloy, CoPt, a CoPt alloy, a Co/Pt multilayer or a Co/Pd multilayer.
 16. The apparatus of claim 14, wherein the interlayer further comprises at least one of Al₂O₃, SiO₂, WO₃, Ta₂O₅, Nb₂O₅, ZrO₂, SiN, NiP, TiN, FeCoB, CoZrNi, and CoTaFe.
 17. The apparatus of claim 14, wherein the interlayer further comprises Ru or an Ru alloy.
 18. The apparatus of claim 14, wherein the interlayer has a thermal conductivity of less than about 5 W/(mK).
 19. An apparatus, comprising: a heat assisted magnetic recording head; and a heat assisted magnetic recording medium adjacent the recording head, the medium comprising: a magnetic data storage layer; a heat sink layer; and an interlayer between the magnetic data storage layer and the heat sink layer, the interlayer configured to encourage heat flow from the magnetic data storage layer to the heat sink layer and resist heat flow from the heat sink layer to the magnetic data storage layer.
 20. The apparatus of claim 19, wherein the interlayer comprises MgO. 